Stream functions for detecting if an int or float is available. #4924
Description
That is, a function like intAvailable() or floatAvailable() that indicates whether or not a call to parseInt() or parseFloat() would succeed given the data currently in the stream's buffer. I'd suggest not applying the timeout to these (i.e. not waiting for additional characters to arrive), because part of the point would be to do other things while waiting for an int or float to arrive on the serial port.
This probably depends on having multi-byte look-ahead / peek (https://github.com/arduino/Arduino/issues/1910), which is a larger issue.